Defining LDA in free format RPG

It has been pointed out that this web site lacks a good description of how to retrieve the data from the Local Data Area, LDA, in the post about defining variables in free format RPG. I agree, which is why I have written this about retrieving and updating the LDA.

I am going assume that we all know what the LDA is. If you do not then you can read IBM's definition of what it is.

There are two common ways to bring in and update the data from the LDA in fixed format RPG.

Why is my RPG program not writing to the file?

I have been asked this question a lot recently:

When I am in debug my RPG program does not write to the file. What is wrong?

I have decided to write this post so I can, in the future, refer people here.

Let me give a very simple example RPG program so I can explain what is going on.

Using SQL for message queue data

One of the new enhancements that came with the latest TRS for IBM i 7.3 and 7.2 is a new SQL View: MESSAGE_QUEUE_INFO. This view returns one line for each message in a message queue, in a similar manner to what is returned by the Display Messages command, DSPMSG.

This will allow me to have a way to quickly, and easily, search a message queue for a message. I must have *USE authority to the message queue, and *EXECUTE authority to the library it is in. One thing to remember is that message queues do get full, and when they do messages from them will be deleted. Also certain message queues are cleared when the IBM i partition is IPL-ed. If you are looking for a message that may have been issued sometime ago you might have better luck searching the History log via SQL.

Viewing object authority using a SQL view

One of the new SQL Views added with the latest Technical Refreshes for IBM i, 7.3 TR2 and 7.2 TR6, is going to be very useful to me. Once a year, at audit time, I am asked to produce a list of all objects within the production library list that are not adequately secured. With the new Object Privileges SQL view I can generate all of the information I need in minutes, using a few SQL statements. This is going to save me a lot of time and effort.

The Object Privileges view, OBJECT_PRIVILEGES, like many of the new Views is to be found in the library QSYS2. The information it contains is the same as the information I can generate using in the Display Object Authority command, DSPOBJAUT. Rather than list all of the columns I will list them when I use them in various SQL statements. If you want to see a full list of all the columns visit the link I have provided a link to the IBM documentation for this View at the bottom of this post.

Second parameter added to SQL's LTRIM and RTRIM

As part of the goodies that came with the recent Technical Refreshes, TR, was the addition of a second parameter to SQL's Left trim, LTRIM, and Right trim, RTRIM, built in functions. The second parameter has the same functionality as it does in CL and RPG's trim built in functions, when used trimming particular character from either the left or right of the string.

The syntax of these SQL functions is remarkably similar to that of the CL built in function:

Using SQL to aggregate columns into one returned result

There are times when I have want an easy way to put values from a file, or table, "horizontally" into one column rather than vertically with more than one row.

"Vertical"	"Horizontal"
TYPE THING ANIMAL ELK ANIMAL HAWK ANIMAL MEERKAT ANIMAL ORCA	TYPE THINGS ANIMAL ELK, HAWK, MEERKAT, ORCA, SEA L FRUIT APPLE, FUJI, BLACKBERRY, GRAPEF VEGETABLE SQUASH

Min and Max built in functions added to RPG

A pair of introductions to RPG as part of IBM i 7.3 TR2, and 7.2 TR6, are the minimum and maximum built in functions, %MIN and %MAX. The maximum built in function returns the greatest value in a list of variables and/or values. The minimum returns the lowest value from a list of variables and/or values. Otherwise the way they are defined and the rules governing them are the same.

To use these functions there must be at least two values, and they must be of the same type. What I mean is that all of the values must be some type of numeric, character, date, time, or timestamp. I cannot mix types in the values. Pointers cannot be used.

They are so simple I can go straight to examples of using them. Let me start with a variety of numeric data types:

Change to SQLRPGLE compile listings

Something I have noticed since the installation of IBM i 7.3 TR2 and 7.2 TR6 on the partitions I use, is a change to the compile listings of SQLRPGLE programs.

The process to create an object from a SQLRPGLE source member is a multi-step process:

1. The syntax of the SQL within the source member is checked to ensure it is valid.

Nested data structures in RPG

I am grateful to the folks at RZKH for applying the PTFs for the latest TR for IBM i 7.3, TR2. I started looking at the new features and functions added to RPG as part of this TR and decided to write about those first (Note: Same functions are included in 7.2 TR6 too). There were three additions, the one that first caught my eye was the ability to nest data structures.

Nested data structures are only available when defining data structures in free format RPG. If you are still using fixed format definitions this is another sign from IBM that it is time to move to free format RPG.

Inserting a nested data structure is pretty much as I would have expected, see below.

End of support for IBM i 7.1 announced

Steve Will, chief architect for the IBM i operating system, announced in a tweet today that the end of support, EOS, for release 7.1 will be on April 30, 2018.

How to write data to a multiple member file

Often I get the same question asked by several people, this time I have been asked the same question five times just this week, and I have been told that this is a question people have been asked in interviews:

How do you write data to different members in the same file using RPGLE?
The file has ten members, and you need to write data to the fifth and sixth members in one RPGLE program.

IBM i performance FAQ updated

An updated version IBM's IBM I on Power – Performance FAQ was published today, called a "Spring refresh" by Steve Will the IBM i chief architect.

The What's new in the latest version?, section 1.3 on page 11, lists eight new questions added to the document.

If you are just a programmer type, not dealing with the finer points of tuning a Power server, there are sections to do with optimizing Cobol and RPG too:

• Section 8.14 p57: How do I tune RPG/COBOL application performance and native I/O file access?
• Section 9 p62-68: Database performance
• Section 10 p69-70: RPG/Cobol native I/O

Good stuff to read, learn, and apply to your work.

The document is a PDF file and can be found on IBM's web site here.